DMX cable wiring - 2 universes

[pilchards]

Hello all,

I'm busy wiring DMX cables that go underfloor.
There will be two universes, so I'm wiring all 5 pins and we are using two cables.

My questions:

• I know where the data + and - go, but do I make ground for both cables? I'm guessing yes.
• Does it matter if the foil shield is touching the ground? I'm guessing no
  
• Secondly, the house lights remote switch is in the same trunking - will it be a problem? unwanted noise? I'm not using mic cable, I'm using EWI DMX cable. The house lights use AC in the remote control - I discovered that when plugging it in, searching for the plug and shocking myself.

I have not tested it yet because the installation is far from complete

Thanks folks,
Malcs

[Esoteric]

I guess I am not understanding your questions, are you using a separate cable for each DMX run (proper) or trying to do two runs in the same 5 conductor cable (improper)?

[pilchards]

separate DMX cables, but let me be verbose quick..

a simple desk was bought for the dimmer, so I laid the underfloor DMX cable.
another desk for controlling scanners was bought, so I laid another cable.

now our hall gets used by the public and I did not want sound cables to be plugged into the lighting, so I used 5pin sockets. at the control desk there is a 5pin male socket inside the floor-box.
each desk will have a 3core cable .. now please do not shoot me, but it will look like a Y, but it is not!
Two 3core cables coming into one female 5pin connector. can i share the ground?
Two 3core cables running to the stage from a male 5pin socket to a female 5pin socket.
Two 3core cables coming out of one male 5pin connector.
One cable going stage left to the dimmer, the other going stage right to an output box downstage

Hope that helps

[Esoteric]

You can not combine DMX cables in that sense. There must be 1 male plug for every female plug.

[Steve Vanciel]

Originally Posted by pilchards

separate DMX cables,.....
I did not want sound cables to be plugged into the lighting, so I used 5pin sockets.

a) It is OK to run two separate DMX signals through one 5 pin connector, typically via a two-twisted pair with ground cable. The 2 pairs can share the ground. This is a valid configuration per the newer DMX512-A standard and is refered to as EF4 (Enhanced Function 4). The originial DMX512 protocol provided for a second data pair on wires 4 & 5 but did not spell out how to use the second pair. This resulted in some confusion and some manufacturers abused those two wires for non-standard uses. Hence the new definitions.

b) However, if you already have two cables run, you would have more flexibility for your system to put separate connectors on them and avoid any confusion with the special adapters you propose.

c) Using 5-pin XLR connectors to avoid confusion with audio lines is EXACTLY why the 5-pin connector was specified in the DMX512 standard. Unfortunately, too many lighting manufactures have thumbed their noses at the standard and used 3-pin connectors on their gear. Not really saving us all that much money since we now have to have a whole drawer full of 3-to-5 and 5-to-3 adapters!!!

SteveV, ETCP-CEE
Orlando, FL

[Esoteric]

Thanks Steve. I must have missed that part of the 512A stsandard.

[pilchards]

Thank you both for taking the time to reply - really appreciated!

Originally Posted by Steve Vanciel

a) It is OK to run two separate DMX signals through one 5 pin connector, typically via a two-twisted pair with ground cable. The 2 pairs can share the ground. This is a valid configuration per the newer DMX512-A standard and is refered to as EF4 (Enhanced Function 4). The originial DMX512 protocol provided for a second data pair on wires 4 & 5 but did not spell out how to use the second pair. This resulted in some confusion and some manufacturers abused those two wires for non-standard uses. Hence the new definitions.

So controller A can then share controller B's ground? (I don't wish to break something)
Controller A is a Chauvet Stage Design 50;
Controller B is a JB Scan Master SM1612.

Originally Posted by Steve Vanciel

b) However, if you already have two cables run, you would have more flexibility for your system to put separate connectors on them and avoid any confusion with the special adapters you propose.

I'd have loved to do that, but space is limited!
If MY adapter is not used, then a desk with a 3pin to 5pin converter can still control the dimmer.

Is it best to keep the amount of connectors to a minimum? like rather have one 10m cable instead of two 5m cables

[pilchards]

Another question [derived] from my first post:
Can DMX cable be next to power cable (240V AC) in parallel? any cons with that?

[Esoteric]

Yes, according to what Steve laid out (haven't been able to go to the protocol yet and look up any guidelines) they can share a ground.

We run our DMX cable in 1/2" grounded conduit (then again we use CAT5 cable), but I am not sure how susceptible it is to interference. But I know that running data (or mic) lines parallel to any power lines is always advised against.

There is really no disadvantage to using 2 5m cables as opposed to 1 10m cable (assuming the connectors are connected well and not stressed).

[pilchards]

Thanks Mike.

Well I cant avoid the power line issue, but I have the option to use a metal conduit instead of a plastic conduit - does it make a real difference? I'd think that the metal would add extra shielding.

OR should I spend extra money on a longer cable to go out from the dimmer and go to the other side of the stage where there will not be any power lines? See attachment

Our sound guy would prefer using one cable, but that's analogue signal. i was just wondering if there was any difference.

See attachment.
The blue box is the dimmer and patch cabinet;
The brown lines are the power lines - each can be patched either to the dimmer or to clean power;
The red lines are the two DMX cables;
The purple points are where splitters or a daisy-chain arrangement will be - I am punting for splitters, dont want to make too many DMX cables!
The dark cyan points are the power sockets;
The yellow is a projector, with a screen - but that's useless info... the projector sits above the audience

[waynehoskins]

If it were me, I'd go for a multiple-output opto-splitter at a central location (control booth, dimmer rack) like an ETC Response Splitter, and then make home runs to each position. Interference from power shouldn't be an issue to worry much about, I don't think.

[Esoteric]

I always put my dmx cable in grounded metal conduit.

You could just avoid the power lines as well. But if you were going to run conduit anyway, why not.

Yeah Wayne I usually use splitters, but it depends on what the lighting positions look like as to how many I use.